How to Install a Reverse Osmosis System

Posted by
John Woodard on June 14, 2024

One of the downsides many homeowners associate with reverse osmosis systems is a more complicated installation process than other home water treatment systems. However, DIY RO installation does not need to be a roadblock between your home and high-quality water. In this article, you can learn what you need to know before installing an RO system and how to install a system under your sink step by step.

Where is a reverse osmosis system installed?

Most reverse osmosis systems are point-of-use systems, meaning they attach to a single outlet of water. In most cases, these are installed underneath the kitchen sink. Note that RO systems utilize a separate faucet, so you will need to drill a hole in your countertop or sink to accommodate this feature if you do not have a hole already drilled. Because RO installation requires modifications to your countertop and because they use more water than other treatment methods, most landlords do not allow reverse osmosis systems to be installed in their rental units.

Learn more: What are the best water filters for apartments and condos?

The video below is made specifically for the installation of Neo-Pure PRO-4 series reverse osmosis systems, but it can also act as a general guide for installing other systems. Regardless of the system you choose, always consult the manufacturer’s instructions for specific installation instructions.

What to know before you purchase a system

You should take a few factors into account before purchasing a reverse osmosis system. These include variables that affect the efficacy of your system and the quality of the treated water.

System size

Before you purchase an RO system, you should know the dimensions of the available space underneath your sink. Once you know your available space, you can select a system that your under-sink area can accommodate. Ensure that you have ample room for the membranes, tank, and installing tubing and fittings.

Water quality

You should also take into account your incoming water quality to determine if certain factors may affect the performance of your reverse osmosis system. For example, high TDS and water hardness greatly increase the rejection rate of the RO membrane. Installing appropriate pre-treatment for an RO system can significantly enhance its performance.

Learn more: What is TDS in water and why should you measure it?

Water pressure

Your home’s water pressure also plays a large role in the efficiency of your RO system. 60 psi is generally considered the ideal pressure for efficient RO water production, but both the pressure from your storage tank and your water’s TDS content play a role in diminishing the pressure inside the system. Osmotic pressure is the natural force that creates osmosis. For reverse osmosis to work, osmotic pressure must be overcome. The higher the TDS levels in your water, the higher the osmotic pressure will be. For every 100 ppm of TDS in your water, 1 additional psi of osmotic pressure must be overcome. This makes appropriate pretreatment or a reverse osmosis booster pump essential in effective RO water treatment.

Learn more: What is a reverse osmosis system?  | What is a reverse osmosis booster pump?

Waste water

Reverse osmosis systems are notorious for wasting water in the treatment process. If you wish to greatly reduce the amount of water wasted by your system, select an RO unit that includes a permeate pump. These pumps utilize the energy of the waste water to propel the treated water, also known as permeate, to the storage tank. Permeate pumps can reduce your system’s waste by up to 80%.

Learn more: How a permeate pump works in a reverse osmosis system

Tools needed to install a reverse osmosis system

Before you begin the installation process, gather the necessary tools to complete the installation and check that you have received all items that are included with the system. The tools you need for a successful installation may vary by system, but you will typically need the following items:

  • Adjustable wrench
  • Drill
  • Phillips head screwdriver
  • Appropriately sized drill bits (vary depending on system)
  • Teflon tape

The material of your countertop determines what type of drill bit is best to use. If you have a granite, quartz, or another type of countertop that splits easily, you will likely want to consult a professional to drill the hole for you. These types of countertops require diamond hole drill bits to prevent damage to the countertop.

How to install a reverse osmosis system

Once you have all the appropriate tools on hand, you are ready to install your system. Note that any time you are using a threaded connection, you should add teflon tape to the threads to create a seal. Avoid covering the first thread with teflon tape to prevent the path of water flow from becoming blocked.

1.  Clear room under the sink.

Ensure that you have access to the drainpipe and cold water shut-off valve. You will also need room to connect all tubing needed for your system.

2.  Turn off the cold water line.

Before you begin installing your system, you must turn off the cold water supply. Once the valve has been turned off, turn on the cold water faucet to relieve pressure in the line.

turning off cold-water valve

3.  Drill the faucet hole.

You must decide if you wish to drill a hole in the sink or in the countertop. Before drilling, ensure that the location of the hole will not interfere with anything beneath the sink. Consult the instructions provided by your RO system’s manufacturer to determine the size of the hole that should be drilled and to clarify any other faucet installation steps.

In some cases, there will already be a covered hole drilled into the countertop, meaning you can skip this step altogether.

4.  Mount the faucet.

Now you can insert the faucet stem into the hole you just drilled. Follow the manufacturer’s instructions and utilize all provided mounting hardware to secure the faucet to your sink or countertop. You may wish to secure the tubing to the bottom of the faucet before mounting it to make your life easier later on.

installing faucet base

5.  Install the drain saddle.

The drain saddle allows the connection between the rejected RO water and the drainpipe. To install the drain saddle, you will need to drill a hole in your drainpipe above the p-trap. Before drilling the hole, place the drain saddle around the drainpipe and mark the drilling location with a marker. Drill the appropriately sized hole for your system and fasten the drain saddle once the hole is created.

drilling drainpipe

6.  Install the feed line adapter valve.

With an adjustable wrench, loosen and remove the riser that feeds the cold water side of the faucet. Connect the swivel end of the feed line adapter, or angle stop valve, to the threads of the cold water shut-off valve. Once the adapter is in place, reconnect the riser tube to the top of the adapter. You will later connect tubing from the feed line adapter to the cold water inlet of the RO system.

installing adapter valve

7.  Make tubing connections.

The tubing for your RO system will be color coded to allow for easy and clear connections. Follow the manufacturer’s instructions to install the appropriate tubing to each line. In this step, you will connect tubing from the system to the tank, drainpipe, and faucet. The number and color of tubing connections look different for each system, particularly if it includes a permeate pump or air gap faucet.

connecting tubing

8. Mount the system under the sink.

Use the provided mounting brackets or other mounting hardware to connect your system to the inside of your under-sink compartment. In most installations, the system itself is mounted near the front of the cabinet, and the tank is installed in the rear. The system is typically mounted on the right wall, but feel free to use whichever wall is more convenient for your space. Ensure you have ample space underneath the system to remove the filters and membrane for regular maintenance.

9.  Start up the system.

Now that your system is installed. You must flush the system and check the system to ensure it works properly without leaks. Read below to learn the steps of this process.

How to start up a new reverse osmosis system

Once your installation is complete, you will need to check for leaks and flush the system. The carbon filters and RO membrane must have water run through them before the water can be consumed.

1.  Flush the system.

Before you can begin using your system, you must flush impurities out of the filter cartridges and membrane. You can flush your system by completing the following steps:

  1. Open the feed water supply valve. Ensure that the ball valve on the tank and the faucet are closed. Slowly turn on the feed water supply so that you can cautiously check for leaks.
  2. Turn on the faucet connected to the RO system. This will purge air from the system and lets water flow through the unit. After 10 to 15 minutes, you will see visibly contaminated water dripping from the faucet. Let this water drip for another 10 to 15 minutes before continuing.
  3. Open the ball valve on the RO tank to let it fill. The length of time it will take the tank to fill is determined by the membrane’s output and the size of the tank.
  4. Once the tank is filled, open the faucet until the tank is completely emptied.
  5. Close the faucet and allow the tank to fill again. The system should be drained a total of at least three times before the water can be used.

2.  Check the system’s performance.

Any time you run water through the system during or shortly after the installation process, monitor all fittings and tubing for leaks. Also take note of any odd vibrations or sounds you hear from the system. If you find a leak, shut off the cold water valve and repair the leak. Strange noises may be caused by a variety of factors, such as improper mounting or air within the system.

If you notice a larger amount of waste water going to the drain than expected, you may need to adjust the flow restrictor or add an RO booster pump to increase water pressure.

Learn more: Troubleshooting your reverse osmosis system

3.  Set up a maintenance schedule

Once you are happy with your system’s performance, you should take note of the necessary maintenance frequency of your system. In most cases, RO prefilters and postfilters last between 6 months and 1 year. RO membrane lifespans can vary greatly, with some lasting 1 year and others lasting as many as 5 years. Factors like incoming water quality, the type of membrane, and incoming water pressure determine how much time you will get from your membrane. While pretreatment can add initial cost to your home’s water treatment system, it can elongate the life of your RO system’s components, increasing your water quality and effectively saving you money over time.

Learn more: RO maintenance quick tips


If you have any questions about selecting or installing a reverse osmosis system, please do not hesitate to contact us.

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